For the past several decades, electrical power exchange between a tractor and trailer has been accomplished via a seven wire cable, or so-called "umbilical cord". The seven wire cable and associated seven pin connectors have become standard equipment in the tractor/trailer industry and have provided for the supply of electrical power to various trailer electrical functions such as turn signals, brake lamps, tail lamps, side marker lamps, clearance lamps and dome lamps, as well as a ground reference for the these electrical circuits. In an effort to provide uniformity throughout the industry, the society of automotive engineers (SAE) has promulgated standards for both the seven wire cable (SAE J-1067) and associated seven pin connectors (SAE J-560).
As used hereinafter, the term "tractor" refers to any vehicle having another vehicle in tow, and therefore includes medium or heavy duty trucks, tractor trucks and tractor truck/trailer combinations having a further vehicle or vehicles in tow. The term "trailer" as used hereinafter refers to tractor truck trailers, semi-trailers and the like.
Referring to FIG. 1, an example of a typical prior art electrical connection system 50 for routing electrical power to an electrical trailer system is shown. A tractor 52 includes a tractor ignition system 54 which acts as an electrical power source to provide electrical power to a tractor electrical system 56 when the tractor 52 is in operation. Connected to tractor electrical system 56 are seven electrical lines 58.sub.1, 58.sub.2, . . . , 58.sub.7, which are configured in accordance with SAE J-1067 standards. Electrical lines 58.sub.1, 58.sub.2, . . . , 58.sub.7 extend from tractor electrical system 56 into a connector housing 60, typically referred to as a "tractor nosebox", which is typically attached to an exterior surface of tractor 52. Housing 60 has a seven conductor electrical connector 62 associated therewith, to which electrical lines 58.sub.1, 58.sub.2, . . . , 58.sub.7 are connected in accordance with SAE J-560 standards.
A trailer 64 includes a trailer lighting system 66 which is operable to provide the aforementioned trailer lighting functions. Connected to trailer lighting system 66 are seven electrical lines 68.sub.1, 68.sub.2, . . . , 68.sub.7, which are configured in accordance with SAE J-1067 standards. Electrical lines 68.sub.1, 68.sub.2, . . . , 68.sub.7 extend from trailer lighting system 66 into a connector housing 70, or "trailer nosebox", which is typically attached to an exterior surface of trailer 64. Housing 70 has a seven conductor electrical connector 72 associated therewith, to which electrical lines 58.sub.1, 58.sub.2, . . . , 58.sub.7 are connected in accordance with SAE J-560 standards.
A seven-conductor connector/cable 74, or "umbilical cord", connects tractor electrical connector 62 to trailer electrical connector 72 so that the tractor electrical system 56 controls, and provides electrical power to, the trailer lighting system 66. A typical umbilical cord 74 includes an SAE J-1067 seven wire jacketed cable with an SAE J-560 seven conductor connector connected thereto at each end. SAE J-560 and SAE J-1067 require a white wire, which must be at least a No. 8 gauge insulated wire, to be the main ground wire, and a red wire, which must be at least a No. 10 gauge insulated wire, to be the main power wire. Black, yellow, green, brown and blue wires are also provided as general purpose wires, and must each be at least No. 12 gauge wires.
Recently, technological advances in the tractor/trailer industry have spawned the need for providing the trailer or trailers with additional electrical functions, thereby creating the concept of a "smart trailer". Examples of such functions include anti-lock brakes, electronic suspension control and tire pressure sensing, to name a few, as well as diagnostic control and fault detection of such special purpose trailer functions. Thus far, a variety of systems have been developed to provide the electrical infrastructure required to accommodate and operate these additional trailer functions, which has led to further development of new electrical interfaces operable to transmit both electrical power requirements and data communications between tractors and trailers. Examples of some recent electrical interface designs include electronic circuitry for providing data communication and electrical power routing through multiple J-560 type umbilical cord connectors, through newly developed connectors and cables having more than the standard seven conductor connections, and through the existing seven conductor (J-560/J-1067) electrical interface of FIG. 1.
Although provisions for additional connectors and connector pins may be a viable solution in the short term, this approach is generally a costly solution, particularly since the addition of further functions will require outfitting existing as well as new tractors and trailers with even more connectors and/or connector pins. This approach has the further disadvantage of reducing connector standardization and increasing connector complexity.
An example of one known design utilizing the existing J-560 electrical connector 74 of FIG. 1 to provide data communications and electrical power routing between a tractor and trailer is set forth in U.S. Pat. No. 5,397,924. The design utilizes electronic circuitry to develop a combination multiplexed high speed communication and power link between the tractor and trailer. The design incorporates circuitry for determining whether the tractor is connected, via the J-560 connector, to either a "smart" (multiplexed) trailer or a conventional (non-multiplexed) trailer. If a multiplexed trailer is connected to the tractor, two of the powered electrical wires within the seven wire J-560 connector are used for serial data communications between the tractor and trailer, and the remaining five provide power and ground connections to the trailer electrical systems. If, on the other hand, a non-multiplexed trailer is connected to the tractor, the seven wire J-560 connector is utilized in the conventional fashion, with each of the two communication wires being switched back to its corresponding conventional configuration so that the tractor electrical system controls the trailer lighting system.
Another known design utilizes a single wire communication approach along with switching circuitry operable to convert one of the multipurpose J-1067 wires to a dedicated single communications line upon detection of a "smart" trailer connection to an appropriately outfitted tractor. The dedicated single wire approach utilizes a slower data rate than the two-wire power line communications approach and therefore typically does not suffer from electrical noise problems associated with such two-wire communications.
It is generally considered desirable by owners and operators of heavy duty tractor/trailers to maintain use of the universal J-560 connectors, sockets and associated umbilical cord in connecting a tractor to a trailer, regardless of the trailer configuration. Any other arrangement will require tractors to be outfitted with new electrical connection hardware when hauling "smart" trailers. When hauling conventional trailers, the tractor must either additionally maintain its J-560 electrical connection hardware, or each conventional trailer must be outfitted with the new conventional electrical connection hardware. In any event, requiring new electrical connection hardware on either the tractor or trailer may be too costly and/or too inefficient for heavy duty tractor/trailer owners and operators to implement.
If the universal J-560 style electrical connection hardware is to be used to provide an electrical power and/or communications interface between a tractor and trailer, it must meet several new requirements. First, the interface should include provisions for eliminating, or at least greatly reducing sources of electrical noise such as from electromagnetic interference (EMI). Second, it must be capable of providing adequate electrical power capability between the tractor and trailer while maintaining the capability of operating the trailer lighting functions. For example, the National Highway Transportation and Safety Administration (NHTSA) has recently ruled that all trailers manufactured after March of 1998 must be equipped with a trailer anti-lock brake system (ABS), and that the ABS must have a dedicated power line and a dedicated ground line provided thereto. Third, the interface should have adequate power and communications capability to permit new electrically controlled trailer functions and features to be added without requiring additional electrical connection hardware for either the tractor or trailer.
The first requirement, protection against electrical noise, may be met by the dedicated single wire communications approach, but this approach also requires one of the general purpose J-1067 wires to be dedicated strictly to communications functions.
The second requirement, provision of adequate power capability, may not be met by known prior art systems. For example, the system disclosed in U.S. Pat. No. 5,397,924 requires at least two of the seven J-560 conductors for communication purposes, and the dedicated single wire communications approach requires one of the seven J-560 conductors for such purposes. In either case, the remaining conductors may be inadequate for providing power and ground lines to all of the trailer's loads while maintaining control over the trailer's lighting circuits.
The third requirement, provision of adequate power capability for additional trailer features, likewise does not appear to be met by known prior art systems. With one or more of the seven J-560 conductors dedicated to communications in known prior art systems, and in view of the proliferation of new electrically controlled trailer functions, some requiring dedicated power and ground lines provided by the tractor, it appears unlikely that known prior art systems will be equipped to meet future power/ground line requirements.
A recent government ruling has mandated antilock brakes on all trailers effective Mar. 1, 1998. In addition, a warning system must be in place by March 2001 which requires an illumination means to be mounted in the truck cab, wherein the illumination means is activated whenever a fault condition associated with the trailer ABS exists. Several such systems are known and some such systems are described in U.S. Pat. Nos. 5,090,779 to Kramer, 5,488,352 to Jasper and 5,677,667 to Lesesky et al. However, each of these systems are problematic in that each requires provisions for a cumbersome and/or expensive communication system for transmitting the ABS fault signal to the tractor cab. For example, the Kramer reference requires a communication system operable to transmit an acoustic signal over existing air brake lines between the tractor and trailer, wherein such an acoustic signal carries the ABS fault signal. The Lesesky et al. reference, on the other hand, requires a wireless RF link to be established between tractor and trailer while the Jasper reference requires additional twisted pair communication wiring in the J-1067 cable to form an inductively coupled communication link between tractor and trailer.
What is therefore needed is a simple and inexpensive communications link for establishing communications between a tractor and trailer that utilizes, in a non-disruptive fashion, the existing J-560/J-1067 wiring. Such an arrangement should ideally be generally immune to electrical noise while providing for a maximum number of available general purpose J-1067 wires for use by the trailer lighting system and special purpose trailer electrical systems. In a specific application, such a communication system may be used to communicate ABS fault signals to a tractor warning system operable to activate a warning means in the cab area of the truck to thereby satisfy the March 2001 government mandate.